[llvm-dev] Building with LLVM_PARALLEL_XXX_JOBS

Wed Mar 2 16:42:32 PST 2016

> On Mar 2, 2016, at 4:22 PM, Sedat Dilek <sedat.dilek at gmail.com> wrote:
> 
> I got some more inspirations on how to speedup my build and integrated
> the URLs into my scripts (attached).
> 
> For example to use GOLD as linker or to use '-O3' OptLevel maybe in
> combination with LTO and PGO (using '-O3 -flto -fprofile-use').

LTO *will* slow down dramatically the build.

-- 
Mehdi

> 
> Let's see when the v3.8.0 FINAL is released.
> 
> - Sedat -
> 
> On 3/2/16, Fabio Pagani <pagabuc at gmail.com> wrote:
>> Hey Chris,
>> 
>> Sedat was asking for a way to "to speedup my build" and those blog posts
>> were really helpful to me.
>> Anyway LLVM_DISTRIBUTION_COMPONENTS sounds very cool, hope you will push
>> your code soon!
>> 
>> On Tue, Mar 1, 2016 at 11:32 PM, Chris Bieneman <cbieneman at apple.com>
>> wrote:
>> 
>>> Fabio, the work I was mentioning here is an extension beyond those blog
>>> posts.
>>> 
>>> Some details:
>>> 
>>> * The “almost 40%” number I referred to is a multi-stage clang build.
>>> That
>>> means we build a host-capable compiler, then build the actual compiler we
>>> want to ship.
>>> * I’m at Apple, so points 1 and 2 are already covered (we only use clang,
>>> and ld64 is a fast linker).
>>> * Our system compiler is PGO+LTO’d, but our stage1 isn’t. Stage1 isn’t
>>> because the performance improvement of PGO+LTO is less than the time it
>>> takes to build, and stage1 is basically a throwaway.
>>> * We are using Ninja and CMake, but this configuration isn’t really
>>> significantly faster than autoconf/make, and actually “ninja install” is
>>> slower in my tests than the old autoconf “make install”. The slowdown is
>>> almost entirely due to Ninja’s “all” target being a lot bigger.
>>> * This performance is for clean builds, not incremental so ccache or
>>> shared libraries would not be a valid optimization
>>> * We do use optimized tablegen
>>> * “Build Less” is exactly what the LLVM_DISTRIBUTION_COMPONENTS enables,
>>> just in a friendly wrapper target.
>>> 
>>> -Chris
>>> 
>>> 
>>> 
>>> On Mar 1, 2016, at 1:12 PM, Fabio Pagani <pagabuc at gmail.com> wrote:
>>> 
>>> For faster builds and rebuilds you should definitely read:
>>> 
>>> https://blogs.s-osg.org/an-introduction-to-accelerating-your-build-with-clang/
>>> https://blogs.s-osg.org/a-conclusion-to-accelerating-your-build-with-clang/
>>> 
>>> Hope this helps!
>>> 
>>> On Tue, Mar 1, 2016 at 9:17 PM, ChrisBieneman via llvm-dev <
>>> llvm-dev at lists.llvm.org> wrote:
>>> 
>>>> 
>>>> 
>>>>> On Mar 1, 2016, at 10:01 AM, Mehdi Amini <mehdi.amini at apple.com>
>>>>> wrote:
>>>>> 
>>>>> 
>>>>>> On Mar 1, 2016, at 9:57 AM, Chris Bieneman <cbieneman at apple.com>
>>>> wrote:
>>>>>> 
>>>>>> There are a few notes I'd like to add to this thread.
>>>>>> 
>>>>>> (1) we have a number of places throughout out CMake build where we
>>>>>> use
>>>> features from newer CMakes gated by version checks. Most of these
>>>> features
>>>> are performance or usability related. None of them are correctness.
>>>> Using
>>>> the latest CMake release will often result in faster builds, so I
>>>> encourage
>>>> it.
>>>>>> 
>>>>>> (2) CMake's "install" target will pretty much always be slower from
>>>> clean than the old autoconf/make "install" target. This is because in
>>>> CMake
>>>> "install" depends on "all", and our CMake builds more stuff in "all"
>>>> than
>>>> autoconf did. To help with this or CMake system has lots of convenient
>>>> "install-${name}" targets that support component-based installation. Not
>>>> every component has one of these rules, but if one you need is missing
>>>> let
>>>> me know. I also recently (r261681) added a new option
>>>> (LLVM_DISTRIBUTION_COMPONENTS) that allows you to specify a list of
>>>> components that have custom install targets. It then creates a new
>>>> "install-distribution" target that wraps just the components you want.
>>>> For
>>>> Apple this is almost a 40% speed up over "ninja install".
>>>>> 
>>>>> That sounds great, I want to use it!
>>>>> It would even be more awesome with an description/example in
>>>> docs/CMake.rst :)
>>>> 
>>>> Once I get the last of the kinks worked out for our internal adoption
>>>> I'm
>>>> going to open source our config files that use it.
>>>> 
>>>> I've also made a note to remind myself to document it in docs/CMake.rst.
>>>> I need to do a pass updating that with a bunch of the cool new things
>>>> we're
>>>> doing with CMake. Thanks for the reminder.
>>>> 
>>>> -Chris
>>>> 
>>>>> 
>>>>> --
>>>>> Mehdi
>>>>>> 
>>>>>> On Feb 25, 2016, at 11:08 AM, Sedat Dilek via llvm-dev <
>>>> llvm-dev at lists.llvm.org> wrote:
>>>>>> 
>>>>>>>> Which combination of cmake/ninja versions are you using (latest are
>>>>>>>> v3.4.3 and v1.6.0)?
>>>>>>> 
>>>>>>> With this combination I could reduce build-time down from approx. 3h
>>>>>>> down to 01h20m.
>>>>>>> 
>>>>>>> $ egrep -i 'jobs|ninja' llvm-build/CMakeCache.txt
>>>>>>> //Program used to build from build.ninja files.
>>>>>>> CMAKE_MAKE_PROGRAM:FILEPATH=/opt/cmake/bin/ninja
>>>>>>> //Define the maximum number of concurrent compilation jobs.
>>>>>>> LLVM_PARALLEL_COMPILE_JOBS:STRING=3
>>>>>>> //Define the maximum number of concurrent link jobs.
>>>>>>> LLVM_PARALLEL_LINK_JOBS:STRING=1
>>>>>>> CMAKE_GENERATOR:INTERNAL=Ninja
>>>>>>> 
>>>>>>> $ LC_ALL=C ls -alt
>>>> logs/3.8.0rc3_clang-3-8-0-rc3_cmake-3-4-3_ninja-1-6-0/
>>>>>>> total 360
>>>>>>> drwxr-xr-x 2 wearefam wearefam   4096 Feb 25 19:58 .
>>>>>>> drwxr-xr-x 6 wearefam wearefam   4096 Feb 25 19:58 ..
>>>>>>> -rw-r--r-- 1 wearefam wearefam 130196 Feb 25 19:54
>>>>>>> install-log_llvm-toolchain-3.8.0rc3.txt
>>>>>>> -rw-r--r-- 1 wearefam wearefam 205762 Feb 25 19:51
>>>>>>> build-log_llvm-toolchain-3.8.0rc3.txt
>>>>>>> -rw-r--r-- 1 wearefam wearefam  14331 Feb 25 18:30
>>>>>>> configure-log_llvm-toolchain-3.8.0rc3.txt
>>>>>>> 
>>>>>>> $ LC_ALL=C du -s -m llvm* /opt/llvm-toolchain-3.8.0rc3
>>>>>>> 315     llvm
>>>>>>> 941     llvm-build
>>>>>>> 609     /opt/llvm-toolchain-3.8.0rc3
>>>>>>> 
>>>>>>> - Sedat -
>>>>>>> 
>>>>>>> [1] https://cmake.org/files/v3.5/cmake-3.5.0-rc3-Linux-x86_64.tar.gz
>>>>>>> _______________________________________________
>>>>>>> LLVM Developers mailing list
>>>>>>> llvm-dev at lists.llvm.org
>>>>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>>> 
>>>> _______________________________________________
>>>> LLVM Developers mailing list
>>>> llvm-dev at lists.llvm.org
>>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>>> 
>>> 
>>> 
>>> 
>> 
> <build_llvm-toolchain_clang-cmake-ninja.sh><install_llvm-toolchain_clang-cmake-ninja.sh>